Synthetic cooking oils containing dicarboxylic acid esters

ABSTRACT

Diesters of the formula ##STR1## wherein R 1  and R 2  are hydrogen or alkyl of from 1 to about 20 carbon atoms, and X and Y are alkyl, alkenyl or .[.dienyl.]. .Iadd.alkadienyl .Iaddend.of from about 12 to about 18 carbon atoms, useful as low calorie synthetic oils suitable for consumption by mammals.

FIELD OF THE INVENTION

The present invention relates to the synthesis and use of synthetic oilsas substitutes for animal and vegetable fats and oils in the preparationof foods for human and animal consumption.

BACKGROUND OF THE INVENTION

Lipids (fats and oils) constitute between 30 and 40% of the caloricintake of the average American diet. Dietary fat, consisting oftriglycerides, is digested to free fatty acids and monoglycerides,primarily in the small intestine. The α-lipase steapsin cleaves theglycerol esters at the 1- and 3-positions. Fatty acids of 6 to 10carbons and unsaturated fatty acids are rapidly absorbed, while those of12 to 18 carbons are absorbed more slowly. Absorption of theβ-monoglycerides by the mucosa of the small intestine results in a finaldigestion and absorption of up to 95% of the total dietary fat. Sincefats yield about twice the energy per gram of either carbohydrates orproteins, substitution of a nondigestible material for a portion of thenormal dietary fat offers a painless and effective method for control ofobesity, hypertension, and other diseases associated with excessivecaloric intake.

There is considerable evidence that steapsin is an enzyme which isspecific for esters of 1, 3-diols and glycerol. U.S. Pat. No. 2,962,419to Minich describes in vitro tests of pentaerythretol tetracaprylate todemonstrate that there is no hydrolysis of the pentaerythritol ester bypancreatic lipase (steapsin) and a greatly diminished total serum lipidconcentration when the substance was used in place of fat in a typicalrate diet. Canadian Pat. No. 1,106,681 to Trost describes the feeding ofdialkyl glycerol ethers to rats, concluding that the esters weregenerally non-digestible, and tests of sucrose polyester in obese humanvolunteers showed decreased total plasma cholesterol and plasmatriglycerides (Glueck et al., Am. J. Cli. Nutri. 35, 1352 (1982)). U.S.Pat. No. 3,600,186 to Mattson et al. describe the use of fatty acidester compounds having at least 4 fatty acid ester groups for use astriglyceride fat substitutes.

Esters of malonic acid and dialkyl malonic acid, and low molecularweight alcohols are known but are unsuitable for use as vegetable oilsubstitutes due to their low boiling points.

There remains a need for stable synthetic oils which are not readilydigestible in mammals, and which are suitable for use in the productionof low calorie fried and baked products containing starches, and inother foods such as oleomargarine, salad oil and other foods normallycontaining vegetable oils.

SUMMARY OF THE INVENTION

The invention provides esters of the formula ##STR2## wherein R₁ and R₂are hydrogen or alkyl radicals containing from 1 to about 20 carbonatoms, and X and Y are alkyl, alkenyl or .[.dienyl.]. .Iadd.alkadienyl.Iaddend.radicals containing from about 12 to about 18 carbon atoms.These materials are synthetic oils and low melting solids which arehydrolyzed slowly or not at all, by pancreatic lipase. Food productsmade with or fried in these synthetic oils contain less metabolizablelipids and are, therefore, lower in available calories, making themsuitable for use by persons with weight or some lipid controldifficulties.

DETAILED DESCRIPTION OF THE INVENTION

The synthetic edible oils of the present invention are represented bythe formula: ##STR3## wherein R₁ and R₂, which may be the same ordifferent, are hydrogen or alkyl radicals of from 1 to about 20 carbonatoms, e.g., methyl, ethyl, hexadecyl, eicosyl, and the like; and X andY, which may be the same or different, are alkyl, alkenyl or.[.dienyl.]. .Iadd.alkadienyl .Iaddend.radicals of from about 12 toabout 18 carbon atoms, e.g., dodecyl, octadecyl, dodecenyl, oleyl,linoleyl, and the like.

In preferred compounds, at least one of the R groups is an alkyl of from1 to about 20 carbon atoms, the other R group being hydrogen or asimilar alkyl. In particularly preferred compounds, one of the R groupsis hydrogen and the other is an alkyl of about 16 carbon atoms, or bothR groups are alkyls of about 16 carbon atoms.

The radicals X and Y are preferably alkyls of from about 14 to about 18carbon atoms, or alkenyls or .[.dienyls.]. .Iadd.alkadienyls .Iaddend.ofabout 18 carbon atoms.

Particularly preferred compounds are .[.hexadecyl dioleylmalonate anddihexadecyl dioleylmalonate.]. .Iadd.dioleylhexadecylmalonate anddioleyl dihexadecylmalonate.Iaddend..

The compounds of this invention are synthetic organic compounds whichdisplay the physical properties of animal fats and vegetable oils. Theyare liquid or solid at room temperature, depending upon molecular weightand structure, and oils at normal cooking temperatures. Unlikenaturally-occurring fats and oils, which are triglycerides (fatty acidesters of glycerol) the products of this invention are fatty alcoholderivatives of malonic acid, and mono- and dialkyl malonic acid. Unliketriglycerides, these compounds resist hydrolysis by pancreatic lipaseand other components of the digestive juices present in the stomach andsmall intestine. As a result, most of the material is not absorbed bythe small intestine.

Examples of fatty alcohols suitable for the practice of this inventioninclude oleyl, myristic, linoleic, palmitic and stearic alcohols, witholeyl alcohol being particularly preferred. They are readily availablecommercially, and readily synthesized by reduction of the correspondingfatty acid obtained by the saponification of fats and oils. Suitableacids include malonic acid, monoalkyl and dialkyl malonic acid, such ashexadecyl malonic acid and dihexadecyl malonic acid. Both the pure,symmetric diesters and mixed esters are suitable, analogous to the mixedesters in naturally-occurring fats and oils.

The synthesis of the compounds of this invention may be accomplished byseveral pathways. For example, certain compounds of the invention may beprepared by reacting a malonyl dihalide with a fatty alcohol or amixture of fatty alcohols. If desired, the product may then be reactedwith an alkyl halide, or a mixture of alkyl halides, in a basic solutionto produce a product of higher molecular weight with a correspondinglyhigher melting point and boiling point.

Impurities may be removed from the esters formed by the above proceduresby vacuum distillation or silica gel chromatography using conventionalequipment and techniques familiar to those experienced in the chemicalarts.

The lower molecular weight compounds of the present invention aresuitable as substitutes for natural oils in spreads such as a mayonnaiseand margarine, and other food products which are not subject to hightemperatures for long periods of time. Higher molecular weight compoundsare preferred for use as synthetic frying oils.

The synthetic oils of the present invention may also comprise mixturesof the disclosed compounds.

Particularly preferred synthetic oils of the present invention have amelting point below about 10° C., a boiling point above about 230° C.,are absorbed by the small intestine of a mammal at a substantially lowerrate than corn oil, and/or provide substantially fewer calories thancorn oil when consumed by a mammal.

Food products fried in synthetic oils of the present invention have alower metabolic fat content than a similar product cooked in animal fator vegetable oil. Similarly, food products in which their normal contentof animal fat or vegetable oil has been partially or completelysubstituted by the synthetic oils of this invention have a lowermetabolic fat content than similar products not containing syntheticoil.

The invention is further illustrated by the following example, which isnot intended to be limiting.

EXAMPLE 1 Preparation of .[.Hexadecyl Dioleylmalonate and DihexadecylDioleylmalonate.].0 .Iadd.Dioleylhexadecylmalonate and DioleylDihexadecylmalonate .Iaddend.

Three molar equivalents of 1-bromohexadecane (available from FlukaChemical Corporation), one molar equivalent of dioleylmalonate (preparedby the reaction of malonyl dichloride (Aldrich) with oleyl alcohol(Aldrich), 0.1 molar equivalent of tetra-n-butylammonium hydroxide (40%solution in water (Aldrich)), and 2-3-molar equivalents of potassiumhydroxide (50% solution in water) were combined in a flask with a smallamount of water and stirred 2-4 hours at room temperature (20°-25° C.).

Stirring for two hours with two molar equivalents of potassium hydroxideresulted in a mixture containing approximately 67% .[.hexadecyldioleylmalonate and 33% dihexadecyl dioleylmalonate.]..Iadd.Dioleylhexadecylmalonate and 33% dioleyldihexadecylmalonate.Iaddend.. Stirring for four hours with three molarequivalents potassium hydroxide gave a higher proportion (67%) of.].dihexadecyl dioleylmalonate.]. .Iadd.dioleyldihexadecylmalonate.Iaddend.. The two malonic esters were purified byremoval of the aqueous phase by extraction with water, vacuumdistillation to remove unreacted bromohexadecane and oleyl alcoholbyproduct, and silica gel chromatography using petroleum ether.

The .[.dihexadecyl dioleylmalonate.]. .Iadd.dioleyl dihexadecylmalonate.Iaddend.was distinguished by its higher melting point (36°-37° C.),quaternary carbon nmr signal at 56 ppm and molecular ion (1054). The.[.hexadecyl dioleylmalonate.]. .Iadd.dioleylhexadecylmalonate.Iaddend.had a melting point of 28°-29° C., tertiary carbon nmr signalat 52 ppm, and molecular ion (829).

What is claimed is: .[.1. A diester of the formula ##STR4## wherein R₁and R₂, which may be the same or different, are hydrogen or alkyl from 1to 20 carbon atoms, with the proviso that at least one of the R groups,R₁ or R₂, is an alkyl of from 1 to 20 carbon atoms; X is an alkyl,alkenyl or dienyl radical from 12 to 18 carbon atoms, and Y is analkenyl or dienyl radical of from 12 to 18 carbon atoms..]. .[.2. Adiester as claimed in claim 1, wherein one of R₁ and R₂ is hydrogen andthe other is an alkyl of 16 carbon atoms..]. .[.3. A diester as claimedin claim 1, wherein both R₁ and R₂ are alkyl of 16 carbon atoms..].
 4. Adiester .[.as claimed in claim 1,.]. .Iadd.of the formula##STR5##.Iaddend. wherein R₁ and R₂, which may be the same or different,are hydrogen or alkyl of from 1 to 20 carbon atoms, with the provisothat at least one of the R groups, R₁ or R₂, is an alkyl of from 1 to 20carbon atoms, wherein X and Y are both .[.alkenyl or dienyl radicalshaving from 12 to 18 carbon atoms.]. .Iadd.oleyl or linoleylradicals.Iaddend..
 5. The diester of claim 4 wherein one of the groupsR₁ and R₂ is hydrogen and the other is an alkyl of 16 carbon atoms andboth X and Y are .[.alkenyls of 18 carbon atoms.]. .Iadd.oleylradicals.Iaddend..
 6. A diester as claimed in claim.[.1.]..Iadd.4.Iaddend., wherein both R₁ and R₂ are alkyl of 16 carbonatoms and X and Y are both .[.alkenyl or dienyl radicals having from 12to 18 carbon atoms.]..Iadd.oleyl or linoleyl radicals.Iaddend.. Thediester of claim 6 wherein X and Y are .[.alkenyls of 18 carbonatoms.]..Iadd.oleyl radicals.Iaddend..
 8. The compound.[.hexadecyldioleylmalonate.]. .Iadd.dioleylhexadecylmalonate.Iaddend..The compound .[.dihexadecyl dioleylmalonate.]. .Iadd.dioleyldihexadecylmalonate.Iaddend.. .[.10. A synthetic edible oil comprisingone or more compounds of the formula ##STR6## wherein R₁ and R₂, whichmay be the same or different, are hydrogen or alkyl of from 1 to 20carbon atoms, X is an alkyl, alkenyl or dienyl radical of from 12 to 20carbon atoms, and Y is an alkenyl or dienyl radical from 12 to 20 carbonatoms..].
 11. A synthetic edible oil comprising a mixture of.[.hexadecyl dioleylmalonate.]. .Iadd.dioleylhexadecylmalonate.Iaddend.and .[.dihexadecyl dioleylmalonate.]..Iadd.dioleyldihexadecylmalonate.Iaddend.. .Iadd.12. A synthetic edibleoil comprising one or more compounds of the formula: ##STR7##.Iaddend.wherein R₁ and R₂, which may be the same or different are hydrogen oralkyl of from 1 to 20 carbon atoms, and X and Y independently each arean alkenyl or alkadienyl radical having from 12 to 18 carbon atoms..Iadd.13. A synthetic edible oil as claimed in claim 12, wherein one ofR₁ and R₂ is a hydrogen and the other is an alkyl of 16 carbon atoms..Iaddend. .Iadd.14. A synthetic edible oil as claimed in claim 12,wherein both R₁ and R₂ are alkyl of 16 carbon atoms. .Iaddend. .Iadd.15.A synthetic edible oil as claimed in claim 12, wherein both X and Y areoleyl or linoleyl radicals. .Iaddend.